1. Field of the Invention
The present invention relates to a heavy duty hinge for an aircraft service pit lid assembly that is used to provide access to subsurface pits located beneath airport runways, docking areas, and other surfaces across which aircraft travel.
2. Description of the Prior Art
At airports and airfields throughout the world, aircraft ground support electricity, air conditioning, fuel, and other aircraft servicing necessities are provided from pits located beneath the surfaces across which the aircraft travel while on the ground. These pits provide subsurface terminations for aircraft servicing facilities such as fuel lines, electrical power supply lines, air conditioning ducts, and other auxiliary services which are provided to aircraft that are on the ground. The use of subsurface pits serves to reduce the congestion of motorized vehicles and lines running across the aircraft servicing areas that would otherwise exist.
Aircraft servicing pits typically take the form of hollow, fiberglass enclosures that are buried in excavated holes dug beneath aircraft servicing areas. Fuel lines, electrical lines, air conditioning lines and other ground support auxiliary service lines are typically laid down during the construction of the airport or aircraft terminal in trenches that are ultimately filled in. These lines run from the terminal facility to the aircraft servicing pits and are accessible through aircraft servicing pit lid assemblies that are located at atop the pits. The pit lid assemblies employ surrounding frames in which pit lids are mounted by hinges for upward rotation about horizontal axes of rotation.
The pits that are mounted within the pit lid supporting frames are typically hinged for rotation relative to the frames by one or more hinge leaves that project laterally from the structure of the pit. Various hinge pin mechanisms have been employed that permanently attach the pit lid leaves to the surrounding pit lid supporting frames. One highly useful pit lit hinge mounting arrangement of this type is described in prior U.S. application Ser. No. 09/693,507 filed Oct. 23, 2000, presently pending. The disclosure of which is hereby incorporated by reference in its entirety.
In conventional practice pit lids are permanently mounted for hinged movement relative to their surrounding frames. By permanently mounting the lid to the frame the pit lid cannot be torn loose from its mounting, even if subjected to extremely high winds or the direct blast of a jet engine.
There are some instances in which it would be advantageous for a pit lid for a subsurface aircraft servicing pit to be completely removable, however. For example, if an aircraft to be serviced is located directly behind the hinge or hinges of a pit lid for a subsurface aircraft servicing pit, cables and hoses drawn out of the pit must be pulled directly past the pit hinge and into contact therewith. The hoses and cables will frequently snag upon the hinge as they are drawn out of the pit, thus requiring time and attention to free them up. This increases the time and difficulty involved in servicing the aircraft.
At the time of pit installation the likely location of aircraft to be serviced is considered in orienting the pit lid support so as to locate the hinge or hinges where they will create the least interference. However, the docking and maneuvering patterns of aircraft are changed constantly. Therefore, even though the orientation and location of the pit lid hinge may be chosen properly for foreseeable aircraft operations at the time of pit installation, aircraft movement patterns in the vicinity of these subsurface pits often can and do change. Therefore, there is a considerable likelihood that, when a hinged pit lid is opened to permit the withdrawal of hoses and cables for servicing an aircraft, the hinge is likely to be at a location between the pit access opening and the aircraft.
Removable pit lids have been utilized in the past, for example, two-handed pit covers were employed for closing smaller pit openings in aircraft service pits such as the CM-18 steel service pit and the FG-18 fiberglass service pit manufactured by Dabico, Inc., located at 2995 Airway Avenue, Costa Mesa, Calif. 92626. However, one significant difficulty with conventional removable pit covers is that, since they lack a hinge mechanism, they are quite heavy and require considerable strength for removal and repositioning to close the pit access opening. Unlike a hinged pit cover in which a portion of the weight of the lid is transmitted to the hinge pins as the lid is raised, an unhinged pit cover must be bodily lifted upwardly, with the entire weight of the lid carried by the person or persons removing the lid.